The present invention generally relates to video signal reproducing apparatuses for reproducing a recorded video signal from a magnetic recording medium, and more particularly to a video signal reproducing apparatus for reproducing a recorded frequency division multiplexed signal of a frequency modulated luminance signal and a frequency converted carrier chrominance signal from a magnetic recording medium such as a magnetic tape and for obtaining a reproduced color video signal in an original frequency band by performing a multiplexing after a frequency demodulation and a frequency conversion.
For example, a helical scan type video tape recorder (VTR) which employs the low-band conversion color recording and reproducing system is conventionally known as a recording and reproducing apparatus which records and reproduces a frequency division multiplexed signal. According to such a VTR, a color video signal applied to an input terminal is separated into a carrier chrominance signal and a luminance signal in a filter circuit. The separated luminance signal is supplied to a non-linear emphasis circuit which has a non-linear emphasis characteristic and emphasizes the luminance signal with smaller emphasis for larger amplitudes, and is thereafter supplied to a main emphasis circuit which emphasizes a high frequency component with a constant emphasis regardless of the amplitude. An output luminance signal of the main emphasis circuit is supplied to a clipping circuit which clips overshoot and undershoot portions which would cause overmodulation in a frequency modulator which is provided in a subsequent stage. An output luminance signal of the clipping circuit is supplied to the frequency modulator and is modulated into a frequency modulated (FM) luminance signal. The FM luminance signal is passed through a highpass filter wherein a low frequency component is sufficiently attenuated, and is supplied to a first adder.
On the other hand, the separated carrier chrominance signal is frequency-converted into a low frequency band in a carrier chrominance signal processing circuit. An output frequency converted carrier chrominance signal of the carrier chrominance signal processing circuit is passed through a lowpass filter and is supplied to the first adder. In the first adder, the frequency converted carrier chrominance signal is frequency-division-multiplexed with the FM luminance signal into the unoccupied low frequency band of the FM luminance signal. An output frequency division multiplexed signal of the first adder is passed through a recording amplifier and is supplied to rotary heads which successively record the frequency division multiplexed signal on tracks formed obliquely to the longitudinal direction of the magnetic tape.
At the time of the reproduction, the recorded frequency division multiplexed signal on the magnetic tape is reproduced by the rotary heads and is supplied to a filter circuit wherein the reproduced frequency division multiplexed signal is separated into a reproduced FM luminance signal and a reproduced frequency converted carrier chrominance signal. The reproduced FM luminance signal is passed through an equalizer and a limiter and is supplied to a frequency demodulator. An output reproduced luminance signal of the frequency demodulator is passed through a lowpass filter, a noise cancelling circuit which uses correlation in the horizontal scanning lines to cancel noise, a main de-emphasis circuit and a non-linear de-emphasis circuit, and is supplied to a second adder. The reproduced frequency converted carrier chrominance signal is converted into a reproduced carrier chrominance signal in the original frequency band in a frequency converter. The reproduced carrier chrominance signal is passed through a bandpass filter wherein an unwanted frequency component is eliminated, and is supplied to the second adder. Hence, a reproduced color video signal in which the reproduced luminance signal and the reproduced carrier chrominance signal are multiplexed is obtained from the second adder.
In the VTR described heretofore, the large amplitude portion of the luminance signal is clipped by the clipping circuit provided in the luminance signal recording system, and a second order distortion is introduced. In other words, when it is assumed that the luminance signal has a frequency f, a second order distortion having a frequency 2f is generated by the clipping performed in the clipping circuit. When the luminance signal having the second order distortion 2f frequency-modulates an FM carrier having a frequency fc in the frequency modulator, a first lower side band (fc-2f) is generated in the frequency spectrum of the output FM luminance signal of the frequency modulator due to the second order distortion 2f. In the case where the frequency f is 1.5 MHz to 2 MHz and the carrier frequency fc is 4 MHz, for example, the first lower side band (fc-2f) is generated at a frequency position in a vicinity of 0 to 1 MHz which is within the frequency band of 629 kHz.+-.500 kHz of the frequency converted carrier chrominance signal. When the recording and reproduction are carried out with the first lower side band (fc-2f) mixed within the frequency converted carrier chrominance signal, the so-called cross-color phenomenon occurs and the picture quality of the reproduced picture becomes poor. In other words, a detailed portion of the picture will have a color which originally does not exist in the detailed portion of the picture.
Accordingly, in order to reduce the cross-color, the frequency characteristic of the highpass filter provided in the luminance signal recording system is conventionally selected to such a characteristic that the FM luminance signal is greatly attenuated within the frequency band of the frequency converted carrier chrominance signal. As a result, the frequency component (fc-2f) is sufficiently attenuated.
However, when the frequency characteristic of the highpass filter provided in the luminance signal recording system is selected to such a characteristic, the low frequency component of the FM luminance signal is also attenuated by the same highpass filter. For this reason, even the required frequency band of the luminance signal is slightly attenuated, and this resulted in the deterioration of the resolution of the picture. Moreover, even when the recording is carried out by suppressing the frequency component (fc-2f), it has been confirmed experimentally that the frequency component (fc-2f) is generated in the reproduced signal during the magnetic recording and reproducing process, but no measure is conventionally available for eliminating the frequency component (fc-2f) generated in the reproduced signal during the magnetic recording and reproducing process.